Ultrasonic transducers are useful for various applications, including ultrasonic testing methods. Ultrasonic testing equipment is used in a variety of applications such as for measuring flow, determining flaws, measuring thickness, and gauging corrosion. This equipment is used with a variety of materials such as metals, plastics, glass, liquids, and chemicals. One particular type of ultrasonic testing apparatus is a pulser-receiver that uses an ultrasonic transducer.
An ultrasonic transducer includes a crystal, wires from the crystal to a connector, and a lens.
Typical ultrasonic transducers operate in the range of about 500 kHz to 25 MHz. A small diameter beam is difficult to obtain with a good depth of field.
If it is desired to, for example, find a particle in a plate that is 50–100 thousandths of an inch thick, using a flat transducer having a beam of ¼ inch diameter or even a smaller straight beam having beam of ⅛ inch diameter, it is difficult to see a particle that is, for example one thousandth of an inch in diameter (0.001 inch diameter). Even if the particle is found, it is difficult to know where the particle is within the beam.
With a plate (e.g., Aluminum 6061) that is 50 thousandths of an inch thick, and a beam having a focal point that is 4 thousandths diameter, it would take approximately 11 scans to cover the whole plate. This is calculated as follows. The first 5 thousandths of an inch is in a dead zone and can't be seen. 50 thousandths minus 5 thousandths equals 45 thousandths. 4 thousandths (diameter of the beam focal point) goes into 45 thousandths approximately 11 times. There is a 50% overlap, so it takes approximately 22 scans to cover the whole plate. It would be desirable to cover the whole plate with a single scan.
There is a need to have a high frequency ultrasonic transducer that is highly focused with a large depth of field (i.e., larger focal area than 4 thousandths of an inch), and a good depth of field to reduce or eliminate the need to rescan areas at different depths to obtain information at multiple depths.